The bug tracking system of Python was notified of a buffer overflow in Python. Affected versions were 3.10, 3.9, 3.8, 3.7, and 3.6. The code in question is part of the PyCArg_repr() function. This function is called when Python has to evaluate parameters from the ctypes class (i.e. wehn you are using C type variables in your Python code). The overflow can be triggered by using extreme values and letting Python expand the content into a buffer:
case 'd':The %f place-holder is interesting. Using 1.79769e+308 (maximum for double data type) or 1.18973e+4932 (maximum for long double data type) will trigger a buffer overflow. This can be detected by the runtime and lead to an error message aborting the interpreter. In any case it is a good example to always validate input data before processing it. Some applications use components from different programming languages. Whenever data is handed around between functions implemented in different run-time environments, then you have to be extra careful about the data types. Sometimes implicit conversions occur. If conversions between numerical data and strings are performed, then always check the limits on both ends.
sprintf(buffer, "<cparam '%c' (%f)>",
self->tag, self->value.d);
break;
You can do the bounds checks even with arbitrary-precision arithmetic (also called bignum, multiple-precision, or infinite-precision arithmetic). Conversions can be done in confined common data types with less precision. This means to cut off the values and lose precision. Arbitrary-precision arithmetic often can export the data to string representations or other serialisation formats. This means that you have to estimate the size of the result. Java™ offers the BigDecimal and BigInteger classes. The buffer estimate looks like this:
byte[] storedUnscaledBytes = bigDecimal.unscaledValue().toByteArray();This gives you the exported values and its size. The latter needs to be used when using the export with functions using size-limited buffers. Both object size and object needs to be processed together and must not be separated in any further processing step. Check your code for conversions near APIs to external libraries or other components. There might be potential for overflows or conversions errors.
int storedScale = bigDecimal.scale();